Apparatus and method of background temperature calibration

ABSTRACT

A circuit includes a controller configured to determine a calibration state of a circuit, to determine an active mode state of the circuit, and to select a type of calibration operation based on the calibration state. The controller is configured to control timing of the selected type of calibration operation in response to determining the calibration state to correspond to a time when the circuit is not active.

FIELD

The present disclosure is generally related to temperature calibrationof a circuit, and more particularly, to background temperaturecalibration.

BACKGROUND

Circuits that include transmitters and/or receivers may utilizecalibration for transmission and for decoding a received signal.Calibration is commonly performed during manufacturing or on initialdevice power-up. However, temperature variation during operation mayimpact circuit performance.

SUMMARY

In an embodiment, a circuit includes a controller configured todetermine a calibration state of a circuit, to determine an active modestate of the circuit, and to select a type of calibration operationbased on the calibration state. The controller is configured to controltiming of the selected type of calibration operation in response todetermining the calibration state to correspond to a time when thecircuit is not active.

In another embodiment, a method of background calibration of a circuitincludes determining a calibration state of a circuit and selecting atype of calibration from a plurality of calibration types based on thecalibration state. The method further includes performing the selectedtype of calibration when the circuit is not actively transmitting anoutput signal or receiving an input signal.

In still another embodiment, a circuit includes a transceiver circuitand a controller coupled to the transceiver circuit. The controller isconfigured to determine an active mode state of the transceiver circuit,to select one or more calibration operations in response to determiningthe calibration state, and to dynamically schedule performance of theone or more calibration operations for a time when the transceivercircuit is not active.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a circuit configured to perform backgroundtemperature calibration according to an embodiment.

FIG. 2 is a block diagram of a circuit configured to perform backgroundtemperature calibration according to a second embodiment.

FIG. 3 is a block diagram of a circuit configured to perform backgroundtemperature calibration according to a third embodiment.

FIG. 4 is a flow diagram of a method of background temperaturecalibration based on changes in temperature according to an embodiment.

FIG. 5 is a flow diagram of a method of background temperaturecalibration based on timers according to an embodiment.

FIG. 6 is a flow diagram of a method of background temperaturecalibration according to an embodiment.

In the following discussion, the same reference numbers are used in thevarious embodiments to indicate the same or similar elements.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

Embodiments of a circuit are described below that provide temperaturedependent calibrations without disrupting circuit functionality, such astransmitter or receiver functionality. In an example, the circuitdetermines a circuit temperature and then determines whether and whattype of calibration to perform based on one of the size of thetemperature change since the last calibration or the amount of time thathas transpired since the last calibration. In an embodiment, the circuitalso determines an active mode state (such as a transmit/receive state)of the circuit and dynamically delays or schedules performance of acalibration operation for a time when the circuit is not active (such asa time when the circuit is not in an active data receiving ortransmitting state).

In an embodiment, the circuit includes multiple timers that may functionindependently and includes multiple selectable calibration operations,which may be performed independently and in the background (relative toa “foreground” operation, such as a transmit operation or a receiveoperation). The circuit may be configured to perform a calibration of afirst type to calibrate a bias current generator when a first timerexpires. The circuit may be configured to perform a calibration of asecond type to calibrate a voltage controlled oscillator (VCO) when asecond timer expires. The circuit may be configured to perform acalibration of a third type to calibrate another circuit and/or both thebias current generator and the VCO when a third timer expires.

In another embodiment, the circuit performs a temperature measurement,determines the difference between the temperature measurement and aprevious measurement for each calibration type when the type ofcalibration was last performed. The difference represents a temperaturechange since a previous calibration was performed. In one embodiment,the circuit determines temperature changes since each type ofcalibration operation was performed. The temperature change may bereferred to as a difference between the circuit temperature and acalibration temperature (i.e., the circuit temperature when a particularcalibration was performed). The circuit then compares the differences toone or more thresholds to determine whether to perform a calibrationand, if so, what type of calibration to perform. In an example, if afirst difference between the circuit temperature and a first calibrationtemperature associated with a first calibration type is greater than afirst threshold or if a second difference between the temperature and asecond calibration temperature associated with a second calibration typeis less than a second threshold, the circuit temperature is within afirst temperature range, and the circuit performs a first type ofcalibration. If the second difference is more than the second thresholdand a third difference between the temperature and a third calibrationtemperature associated with a third calibration type is less than athird threshold, the circuit temperature is within a second temperaturerange, and the circuit performs a second calibration type. If the thirddifference is greater than 100° C., the circuit temperature is within athird temperature range, and the circuit performs a third calibrationtype. One possible example of a circuit configured to perform backgroundtemperature calibrations is described below with respect to FIG. 1.

FIG. 1 is a block diagram of a circuit 100 configured to performbackground temperature calibration according to an embodiment. As usedherein, the term “background temperature calibration” refers toperformance of the calibration operation during periods when the circuitas a whole or selected components of the circuit 100 are not active. Inone example, background temperature calibration may refer to performanceof one or more calibration operations when a transceiver of circuit 100is not actively transmitting or actively receiving a signal.

Circuit 100 includes a controller 102 coupled to a temperature sensor110, one or more timers 112, and a memory 114. Further, circuit 100includes a voltage regulator 106 coupled to controller 102 and to avoltage controlled oscillator (VCO) 104. Circuit 100 also includes abias current generator 108 coupled to controller 102, voltage regulator106, and VCO 104.

Memory 114 is configured to store data and to store processor-readableinstructions. Controller 102 may be a processor or microcontrollercircuit (MCU) that may execute instructions stored in memory 114. Memory114 stores time thresholds 116, voltage thresholds 118, temperaturethresholds 120, and previous calibration data 122. Further, memory 114stores previous temperature measurement data 124. Memory 114 may alsostore calibration instructions for multiple calibration types 126 that,when executed by controller 102, cause controller 102 to selectivelyperform one or more types of calibrations as background operations. Inan embodiment, controller 102 may dynamically schedule performance ofthe selected types of calibration operations for times when the circuitis not active.

Circuit 100 may further include a transmit/receive circuit 130 that isconfigured to transmit and/or receive data through an antenna (notshown). In an embodiment, transmit/receive circuit 130 may include areceiver including a detector capable of determining the validity of theinput data. In an example, the validity of the input data may bedetermined based on a number of correctly detected preamble bits or syncbits (when the number of bits exceeds a threshold) or based on a networkor device identifier embedded within a received packet. In anembodiment, transmit/receive circuit 130 may include a receiver, atransmitter, or both (i.e., a transceiver). Transmit/receive circuit 130may be coupled to VCO 104 and to controller 102. In an embodiment,controller 102 may determine a transmit/receive state associated withcircuit 100, for example, based on a signal from transmit/receivecircuit 130 and may delay a calibration operation for circuit 100 toavoid performing the calibration while the transmit/receive circuit 130is either sending or receiving data.

In an embodiment, controller 102 may receive a temperature signalcorresponding to a circuit temperature from temperature sensor 112. Inresponse to the temperature signal, controller 102 determines whether toperform a calibration operation and what type of calibration to perform.In an example, controller may determine differences between the circuittemperature and one or more calibration temperatures (which werecaptured when a previous calibration operation was performed). Thedifferences may be compared to one or more thresholds to determinewhether and what type of calibration to perform. Further, controller 102may optionally determine when to perform the calibration operation, suchas when the circuit is not transmitting or receiving.

In an embodiment, controller 102 may determine whether and what type ofcalibration to perform based on a difference between the temperaturemeasurement and the temperature at the time of a last calibration of aparticular type. In another embodiment, controller 102 may determinewhen to perform a calibration based on the difference. In anotherembodiment, controller 102 may delay a calibration operation until atransmit or receive operation is completed. Alternatively, controllermay delay the calibration operation (dynamically schedule performance ofthe calibration operation) for a time when the circuit or a component ofthe circuit is not active.

In an embodiment, memory 114 stores one or more temperature thresholds120. Controller 102 may receive a temperature measurement signal fromtemperature sensor 110, may subtract the temperature measurement fromprevious temperature measurements corresponding to previous calibrationoperations, and may select one of the sets of calibration instructions126 (based on the differences) for execution in order to calibrate acircuit component, such as VCO 104, bias current generator 108, anothercircuit element, or any combination thereof. Alternatively, controller102 may compare one or more timer values to one or more time thresholdsto determine whether and what type of calibration to perform. In anexample, each timer may correspond to a particular type of calibration,and may be reset after controller 102 performs the calibration. In thisalternative example, the calibration may be selected and performed basedon timer expiration without consideration of whether or not thetemperature difference exceeds the threshold.

While the illustrated example of FIG. 1 depicts a simplified example ofa circuit 100 configured to provide a background calibration, it shouldbe appreciated that the background calibration functionality may beincorporated in a variety of circuits, including garage door openers,remote keyless entry systems, home automation and security systems,wireless remote controls, and other transmitter/receiver devices. Thecalibration operation may be used to calibrate timing circuits,analog-to-digital converters (ADCs), digital-to-analog converters(DACs), driver circuitry, oscillators, other circuits, or anycombination thereof. One example of a radio frequency transmittercircuit that includes background calibration functionality is describedbelow with respect to FIG. 2.

FIG. 2 is a block diagram of a circuit 200 configured to performbackground temperature calibration according to a second embodiment.Circuit 200 includes a micro-controller unit (MCU) 202 coupled to aradio frequency (RF) analog core 204 and to a memory 210. In anembodiment, MCU 202 may be configured to execute instructions stored inmemory 210 to control operation of circuit 200. MCU 202, in conjunctionwith instructions stored in memory 210, operates as a controller, suchas controller 102 in FIG. 1. MCU 202 is also coupled to digitalperipherals 206, an output data serializer (ODS) 214, a frequencycounter 216, a temperature demodulator 218, an input/output (I/O)interface 220, and a debug and programming interface (labeled “C2”)through a special function registers bus 212. I/O interface 220 may becoupled to one or more general purpose I/O pads 240 and to a crystaloscillator (labeled “XTAL OSC”) 260 within RF analog core 204.

MCU 202 includes an intelligent random access memory (IRAM) 224, anon-chip register (labeled “XREG”) 226, RAM 228, and a read-only memory(ROM) 230. Memory 210 includes a non-volatile memory (labeled “NVM”) 242and an electrically-erasable programmable read-only memory (EEPROM) 244.User software, stored in NVM 242, may be executed by MCU 202 to controloperation of and interaction with peripherals, and may cause MCU 202 toindividually shut down any or all peripherals for power savings.

Digital peripherals 206 include an interrupt configuration (INTC) 232, areal-time clock (RTC) 234, a timer (TMR) 236, and an advanced encryptionstandard (AES) hardware accelerator 238. RF analog core 204 includes ahigh voltage RAM (HVRAM) 246 coupled to SFR bus 212. RF analog core 204further includes a local oscillator 248 including inputs coupled tofrequency counter 216 and to ODS 214, and an output coupled to a clockdivider 250, which has an output coupled to a power amplifier (PA) 252.PA 252 has two outputs including a first output coupled to atransmit-plus pin or pad and a second output coupled to a transmit-minuspin or pad to provide a differential output signal to an antenna fortransmission. RF analog core 204 further includes a low power oscillator256, a sleep timer 258, and XTAL OSC 260. RF analog core 204 alsoincludes a temperature sensor 112 coupled to SFR bus 212 throughtemperature demodulator 218.

RF analog core 204 includes a low dropout regulator (LDO) 208 includinga power on reset and a bandgap reference to provide internal analog anddigital supplies, VA and VD, respectively. The power-on reset (POR)circuit monitors the power applied to circuit 200 and generates a resetsignal to set circuit 200 into a known state on power-on. The bandgapproduces voltage and current references for the analog blocks in circuit200 and can be shut down when the analog blocks are not used. In anembodiment, LDO 208 may be coupled to MCU 202 and may be responsive tocontrol signals from the MCU 202 and/or to control bits stored in apower register to adjust at least one of a reference voltage and areference current in response to at least one of the control signals andthe control bits.

The on-chip temperature sensor 112 measures the internal temperature ofcircuit 200, and temperature demodulator 218 converts the sensor outputinto a binary number representing temperature. The binary number may beused by MCU 202 to compensate the frequency of the local oscillator whenthe temperature changes based on the devices' frequency response versustemperature calibration.

In an embodiment, MCU 202 receives temperature data from temperaturesensor 112 through temperature demodulator 218 and SFR bus 212. MCU 202may determine how much the temperature has changed since a previouscalibration was performed. In an example, when the temperature changesby more than a first threshold (such as, for example, 20° C.) since thebias current generator 108 was last calibrated, MCU 202 may execute afirst type of calibration operation. In an embodiment, the first type ofcalibration may include a bias calibration. When the temperature changesby more than a second threshold (such as, for example, 60° C.) since theVCO 104 was last calibrated, MCU 202 may execute a second type ofcalibration operation. The second type of calibration may include thebias calibration and/or a VCO calibration. When the temperature changesby more than a third threshold (e.g., 100° C.), MCU 202 may execute athird type of calibration operation. The third type of calibration mayinclude the bias calibration, the VCO calibration, and one or more othercalibrations.

In another embodiment, MCU 202 may be configured to perform a selectedtype of calibration periodically. In an example, MCU 202 may execute afirst calibration type (based on a first set of calibrationinstructions) when a first timer expires, a second calibration type(based on a second set of calibration instructions) when a second timerexpires, and a third calibration type (based on a third set ofcalibration instructions) when a third timer expires. Alternatively, MCU202 may be configured to perform one or more calibration operations whenthe temperature of the circuit exceeds a predetermined temperature.

In an example, MCU 202 may periodically poll the circuit temperature ormay retrieve the circuit temperature in response to an event, such as abutton press event. MCU 202 may determine what type of calibrationoperation to perform and may determine the active mode state of thecircuit, such as whether the circuit is actively transmitting orreceiving. MCU 202 may schedule the calibration to be performed when thecircuit is inactive.

FIG. 3 is a block diagram of an apparatus 300 configured to performbackground temperature calibration according to a third embodiment.Apparatus 300 includes an integrated circuit 302 coupled to a powersource 304, such as a coin battery or other small profile battery.Further, apparatus 300 includes light emitting diode 306 and one or morepush buttons 308, which are coupled to circuit 302. Further, circuit 302is coupled to an antenna, such as a loop antenna. In an embodiment,apparatus 300 may be a remote control transmitter, such as a garage dooropener remote control device.

Circuit 302 includes LDO regulator 208, which is coupled to localoscillator 248, divider circuit 250, and PA 252. Circuit 302 furtherincludes MCU 303, which is one possible implementation of MCU 202 inFIG. 2. MCU 303 is coupled to local oscillator 248, clock divider 250,and PA 252. Further, MCU 303 may be coupled to I/O interface 220, whichmay be coupled to light-emitting diode 306 and to the one or more pushbuttons 308. MCU 303 may be coupled to a temperature sensor 110. In anexample, temperature sensor 110 may be coupled to MCU 303 indirectlythrough a temperature demodulator, such as temperature demodulator 218in FIG. 2. Additionally, MCU 303 may be coupled to RAM/ROM 228/238, NVM242 and EEPRROM 244. In the illustrated example, NVM 242 may includecalibration instructions for a Type 1 Calibration 310, a Type 2Calibration 312, and a Type 3 Calibration 314. Further, NVM 242 maystore one or more temperature thresholds 316, which may be used todetermine whether to recalibrate circuit 302 and/or which type ofcalibration to perform.

In an embodiment, MCU 303 may receive a temperature measurement,determine a change in temperature since the last Type 1, Type 2, andType 3 calibrations, and may perform a selected type of calibrationbased on the change. In another embodiment, if the change in temperatureis greater than a predetermined threshold, MCU 303 may perform aselected type of calibration. In another embodiment, MCU 303 may performa selected type of calibration based on expiration of one or more timersrepresenting a time since the associated type of calibration was lastperformed. In some embodiments, MCU 303 may also delay the calibrationoperation based on an active mode state of the circuit 300. One possibleexample of a method of whether and what type of calibration operation toperform is described below with respect to FIG. 4.

FIG. 4 is a flow diagram of a method 400 of background temperaturecalibration based on changes in temperature according to an embodiment.At 402, the circuit temperature is measured. In an embodiment, MCU 303receives the temperature measurement from temperature sensor 112.Advancing to 404, MCU 303 may then determine a difference between thecircuit temperature and the temperatures at the last times that each ofthe types of calibrations was last performed. For example, if the MCU303 is configured to perform three types of calibrations, then threedifferences may be determined, one for each type of calibration.

Continuing to 406, if the difference between the circuit temperature anda temperature of a last Type 1 calibration is greater than a firstthreshold or the difference between the circuit temperature and thetemperature of a last Type 2 calibration is less than a secondthreshold, the method 400 advances to 408 and MCU 303 performs a Type 1calibration before returning to 402 to measure the circuit temperatureagain. In an embodiment, a first threshold may be 20° C. and a secondthreshold may be 60° C. If, at 406, the difference between the circuittemperature and the temperature of the last Type 1 calibration is notgreater than the first threshold or the difference between the circuittemperature and the temperature of the last Type 2 calibration is notless than the second threshold, the method 400 advances to 410.

At 410, if the difference between the circuit temperature and thetemperature of the last Type 2 calibration is greater than the secondthreshold or the difference between the circuit temperature and thetemperature of the last Type 3 calibration is less than a thirdthreshold, method 400 advances to 412 and MCU 303 performs a Type 2calibration operation before returning to 402 to measure the circuittemperature again. In an embodiment, the third threshold may be 100° C.If, at 410, the differences are not between the second and thirdthresholds, method 400 advances to 414. At 414, MCU 303 determines ifthe difference between the circuit temperature and the temperature atthe time of a last Type 3 calibration is greater than the thirdthreshold. If so, method 400 advances to 416 and MCU 303 performs a Type3 calibration and then returns to 402 to measure the temperature again.Otherwise, at 414, if the difference is less than the third threshold,method 400 returns to 402 to measure the temperature again.

In an embodiment, the first calibration type may include adjusting abias circuit, such as adjusting one or more voltages or currents,configuring a switch network, or otherwise adjusting a circuit tocompensate for performance variation due to temperature. The secondcalibration type may include adjusting timing of a voltage controlledoscillator to compensate for performance variation due to temperature.The third calibration type may include adjusting another circuitparameter to compensate for temperature-based performance variation.

In an example, performance of the various calibrations at 408, 412, and416 may be delayed so as to avoid interruption of various circuitoperations. In one example, the selected calibration may be scheduled toavoid interruption of a transmit or receive operation. Thus, thecalibration may be performed in the background as opposed to calibrationbeing performed as a foreground operation that interrupts or delaysother circuit operations.

In the illustrated example of FIG. 4, MCU 303 may control which type ofcalibration to perform based on the difference between the circuittemperature and the circuit temperature at the last calibrationoperation for each calibration type. Thus, MCU 303 uses the circuittemperature to determine whether to perform a calibration operationand/or which type of calibration operation to perform.

While the above-described method 400 uses temperature to determinewhether and when to perform a calibration operation. It is also possibleto perform each type of calibration periodically. One possible exampleof a method of performing periodic calibrations of different types isdescribed below with respect to FIG. 5.

FIG. 5 is a flow diagram of a method 500 of background temperaturecalibration based on timers according to an embodiment. At 502, MCU 303sets a timer for calibration. Circuit 300 may include multiple timers,one for each type of calibration, and MCU 303 may be configured toinitialize all of the timers on power-up and subsequently to resetindividual timers after a particular type of calibration is performed.

Advancing to 504, if a first timer (Timer 1) is expired, method 500continues to 506 and MCU 303 performs a Type 1 calibration beforereturning to 502 to reset the first timer. In an example, the firsttimer may represent a time since the last Type 1 calibration wasperformed. If at 504, the first timer is not expired, method 500advances to 508 to determine if the second timer (Timer 2) is expired.If the second timer is expired, method 500 advances to 510, and MCU 303performs a Type 2 calibration before returning to 502 to reset thesecond timer. If, at 508, the second timer has not expired, method 500advances to 512 to determine if the third timer (Timer 3) is expired. Ifthe third timer is expired, method 500 continues to 514 and MCU 303performs a Type 3 calibration before returning to 502 to reset the thirdtimer. Otherwise, at 512, if the third timer is not expired, method 500returns to 504 to determine if the first timer is expired.

In each instance, method 500 may also include determining atransmission/reception state or some other state of the circuit prior toperforming the selected calibration operation to prevent the calibrationfrom interrupting another circuit operation. One possible example of amethod of scheduling the calibration for a time when the circuit is nottransmitting or receiving is described below with respect to FIG. 6.

FIG. 6 is a flow diagram of a method 600 of background temperaturecalibration according to an embodiment. Advancing to 602, a calibrationstate is determined. In an example, the MCU 303 determines whether acalibration should be run and, if so, what type of calibration. Thedetermination may be based on expiration of a timer and/or a change inthe circuit temperature.

Proceeding to 604, if no calibration is needed, method 600 returns to602 and the calibration is state is determined. Otherwise, at 604, if acalibration should be performed based on temperature or time, method 600continues to 606 and MCU 303 determines if a transmit state of thecircuit indicates that the circuit is transmitting. If the circuit istransmitting, method 600 returns to 604 to determine if a calibrationshould be performed. In an example, the MCU 303 may stall thecalibration operation until the transmission is over. If, at 606, thecircuit is not transmitting, method 600 advances to 608 to determine ifa receive state of the circuit indicates that the circuit is receiving.If not, method 600 advances to 612 and MCU 303 calibrates the circuitbefore returning to 602.

However, if at 608 the circuit is receiving, method 600 advances to 610and the MCU 303 determines if preamble bits are detected or if packetreception is in progress. Detection of preamble bits represents onepossible method to indicate the reception of a valid packet, i.e.,active reception of a packet. By checking a detector for pre-amble bits,the transceiver (or MCU 303) can determine if a valid packet iscurrently in progress. Additionally, other indicators of a packet mayinclude detection of a sync word (a special synchronization string ofdata) or other identifiers for a valid packet such as MAC (Media AccessControl) address, IP (Internet Protocol) address or any type of networkor device address. If so, method 600 holds at 610 until no preamble bitsor no packets are detected or a packet in progress has been completed.At 610, if there are no preamble bits detected or no packet in progress,method 600 proceeds to 612 and MCU 303 calibrates the circuit.

In the above-discussion of FIGS. 4-6, some of the methods were describedwith respect to MCU 303. It should be appreciated that such operationsmay be performed using controller 102 in FIG. 1 or MCU 202 in FIG. 2,depending on the implementation. Further, the arrangement of the blocksin methods 400, 500 and 600 in FIGS. 4, 5, and 6 may be altered withoutdeviating from the spirit of the disclosure. For example, in FIG. 6, thereceive state (block 608) may be determined before the transmit state(block 606).

In accordance with various embodiments, the methods described herein maybe implemented as one or more processor-readable instruction setsexecuting on a processor, microcontroller unit (MCU), field programmablegate array (FPGA), or other circuit. In accordance with anotherembodiment, the methods described herein may be implemented as one ormore user-programs running on an electronic device, such as a garagedoor opener, a remote control, or other transmitting or receivingdevice. Dedicated hardware implementations including, but not limitedto, application specific integrated circuits, programmable logic arrays,and other hardware devices can likewise be constructed to implement themethods described herein.

The illustrations, examples, and embodiments described herein areintended to provide a general understanding of the structure of variousembodiments. The illustrations are not intended to serve as a completedescription of all of the elements and features of apparatus and systemsthat utilize the structures or methods described herein. Many otherembodiments may be apparent to those of skill in the art upon reviewingthe disclosure. Other embodiments may be utilized and derived from thedisclosure, such that structural and logical substitutions and changesmay be made without departing from the scope of the disclosure.Moreover, although specific embodiments have been illustrated anddescribed herein, it should be appreciated that any subsequentarrangement designed to achieve the same or similar purpose may besubstituted for the specific embodiments shown.

This disclosure is intended to cover any and all subsequent adaptationsor variations of various embodiments. Combinations of the aboveexamples, and other embodiments not specifically described herein, willbe apparent to those of skill in the art upon reviewing the description.Additionally, the illustrations are merely representational and may notbe drawn to scale. Certain proportions within the illustrations may beexaggerated, while other proportions may be reduced. Accordingly, thedisclosure and the figures are to be regarded as illustrative and notrestrictive.

What is claimed is:
 1. A circuit comprises: a timer coupled to acontroller; and the controller configured to determine a calibrationstate of the circuit, to determine an active mode state of the circuit,to select a type of calibration operation based on the calibrationstate, and to control timing of the selected type of calibrationoperation in response to determining the calibration state to correspondto a time when the circuit is not active, the controller is configuredto perform: a first type of calibration when the timer exceeds a firstthreshold; a second type of calibration when the timer exceeds a secondthreshold; and a third type of calibration when the timer exceeds athird threshold.
 2. The circuit of claim 1, further including atemperature sensor coupled to the controller and configured to provide asignal representing a circuit temperature to the controller.
 3. Thecircuit of claim 2, wherein the controller determines a calibrationstate of the circuit by calculating a difference between the circuittemperature and at least one previously recorded temperaturecorresponding to previously performed type of calibration, thecontroller configured to perform one or more calibration operations whenthe difference exceeds a threshold temperature.
 4. The circuit of claim3, wherein the controller is configured to perform: a first type ofcalibration when the difference is greater than a first threshold andless than a second threshold; and a second type of calibration when thedifference is greater than the second threshold and less than a thirdthreshold.
 5. The circuit of claim 1, wherein the selected type ofcalibration comprises at least one of a bias circuit calibration and avoltage controlled oscillator calibration.
 6. The circuit of claim 1,wherein the active mode state comprises at least one of a transmittingmode state and a receiving mode state.
 7. The circuit of claim 6,further comprising a receiver including a detector configured todetermine validity of input data received by the receiver; and wherein areceive mode state of the circuit is determined by the detector based onthe validity of the input data.
 8. The circuit of claim 7, wherein thedetector determines the validity of the input data when a number ofcorrectly detected preamble bits or sync bits exceeds a threshold. 9.The circuit of claim 7, wherein the detector determines the validity ofthe input data based on at least one of a network identifier and adevice identifier embedded within a packet.
 10. A circuit comprising: acontroller configured to determine a calibration state of a circuit, todetermine an active mode state of the circuit including at least one ofa transmitting mode state and a receiving mode state, to select a typeof calibration operation based on the calibration state, and to controltiming of the selected type of calibration operation in response todetermining the calibration state to correspond to a time when thecircuit is not active; and a receiver including a detector configured todetermine a receive mode state of the receiver based on validity ofinput data received by the receiver.
 11. The circuit of claim 10,further including a temperature sensor coupled to the controller andconfigured to provide a signal representing a circuit temperature to thecontroller.
 12. The circuit of claim 11, wherein the controllerdetermines a calibration state of the circuit by calculating adifference between the circuit temperature and at least one previouslyrecorded temperature corresponding to previously performed type ofcalibration, the controller configured to perform one or morecalibration operations when the difference exceeds a thresholdtemperature.
 13. The circuit of claim 12, wherein the controller isconfigured to perform: a first type of calibration when the differenceis greater than a first threshold and less than a second threshold; anda second type of calibration when the difference is greater than thesecond threshold and less than a third threshold.
 14. The circuit ofclaim 10, wherein the selected type of calibration comprises at leastone of a bias circuit calibration and a voltage controlled oscillatorcalibration.
 15. The circuit of claim 10, further comprising: a timercoupled to the controller; and wherein the controller is configured toperform: a first type of calibration when the timer exceeds a firstthreshold; a second type of calibration when the timer exceeds a secondthreshold; and a third type of calibration when the timer exceeds athird threshold.
 16. The circuit of claim 10, wherein the detectordetermines the validity of the input data when a number of correctlydetected preamble bits or sync bits exceeds a threshold.
 17. The circuitof claim 10, wherein the detector determines the validity of the inputdata based on at least one of a network identifier and a deviceidentifier embedded within a packet.
 18. A circuit comprising: a timercoupled to the controller; and a controller configured to determine acalibration state of a circuit, to determine an active mode state of thecircuit including at least one of a transmitting mode state and areceiving mode state, to select a type of calibration operation based onthe calibration state, and to control timing of the selected type ofcalibration operation in response to determining the calibration stateto correspond to a time when the circuit is not active, the controlleris configured to perform: a first type of calibration when the timerexceeds a first threshold; a second type of calibration when the timerexceeds a second threshold; and a third type of calibration when thetimer exceeds a third threshold.
 19. The circuit of claim 18, furthercomprising a receiver including a detector configured to determinevalidity of input data received by the receiver; and wherein a receivemode state of the circuit is determined by the detector based on thevalidity of the input data; wherein the detector determines the validityof the input data based on at least one of: when a number of correctlydetected preamble bits or sync bits exceeds a threshold; and at leastone of a network identifier and a device identifier embedded within apacket.
 20. The circuit of claim 18, further comprising: a temperaturesensor coupled to the controller and configured to provide a signalrepresenting a circuit temperature to the controller; and wherein thecontroller: determines a calibration state of the circuit by calculatinga difference between the circuit temperature and at least one previouslyrecorded temperature corresponding to previously performed type ofcalibration, the controller configured to perform one or morecalibration operations when the difference exceeds a thresholdtemperature; performs a first type of calibration when the difference isgreater than a first threshold and less than a second threshold; andperforms a second type of calibration when the difference is greaterthan the second threshold and less than a third threshold.